JPH08201326A - Exhaust co concentration detecting device for combustion apparatus - Google Patents

Abstract

PURPOSE: To provide an exhaust CO concentration detecting device for a combustion device detecting the accurate CO concentration in the exhaust gas regardless of the type of a fuel. CONSTITUTION: The ratio between the CO concentration constituent and the H2 concentration constituent contained in the sensor output of a CO sensor 13 is constant regardless of the type of a fuel for each operating temperature of the CO sensor 13. An arithmetic equation for calculating the true CO concentration based on the ratio between the CO and H2 concentration constituents contained in the sensor outputs of CO sensors 13A, 13B having different operating temperatures is introduced, and this arithmetic equation is applied to a CO concentration determining arithmetic section 15. A sensor drive controller 14 excites and heats the CO sensors 13A, 13B at different set temperatures respectively. The CO concentration determining arithmetic section 15 receives the outputs of the CO sensors 13A, 13B, substitutes them into the arithmetic equation, and calculates and outputs the true CO concentration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CO gas (carbon monoxide gas) contained in an exhaust gas of a combustion device installed in the combustion device.
The present invention relates to an exhaust CO concentration detection device for a combustion device that correctly detects the concentration of CO.

[0002]

2. Description of the Related Art CO is provided on the exhaust side of combustion equipment such as a water heater.
A CO detection sensor is provided in order to prevent danger due to generation of gas.

An example of a catalytic combustion reaction type CO sensor generally known as this type of CO detection sensor is shown in FIGS. 4 and 5. In these figures, the base 1
Two pairs of terminal pins 2 are provided on the upper surface of the device, and a comparison element 4 which is insensitive to CO gas and a detection element which is sensitive to CO gas are provided through a thin platinum wire 3 having a diameter of several 10 μm between each pair of terminal pins. 5 is provided, and the comparison element 4 and the detection element 5 are separated by a partition plate 6. The detecting element 5 has C
It contains a catalyst that causes a combustion reaction with O 2 gas.

Around these comparison element 4 and detection element 5,
It is covered with a cylindrical glass wool 7 having open upper and lower end surfaces, and the outer side thereof is covered with a metal cover 8. A blade-shaped plate 10 is formed by cutting and raising on the inner surface of the peripheral wall of the metal cover 8, and the exhaust gas is formed so as to enter the inside through a cut-and-raising opening 11.

The comparison element 4 and the detection element 5 are incorporated in a resistance bridge circuit as shown in FIG. The comparison element 4 and the detection element 5 perform the CO gas detection period, that is, during the combustion of the combustion equipment and the post-purge period of about 5 minutes after the combustion is stopped (the period when the combustion fan is continuously rotated after the combustion is stopped). , In order to keep the element operation stable, it is heated to about 200 ℃ by energization. In this state, when CO gas comes into contact with the detection element 5, a catalytic combustion reaction occurs, and this reaction causes the temperature of the detection element 5 to rise. It rises and electric resistance increases. Due to this resistance change, the equilibrium state of the bridge circuit is lost, and the current change due to the loss of balance is converted into a voltage change, which is taken out as a CO detection signal.

Generally, the sensor output of the CO sensor depends on the CO concentration and the hydrogen gas (H ₂ gas) concentration in the exhaust gas. As described above, the sensor output of the H ₂ gas is added to the sensor output of the CO concentration in the exhaust gas, which results in a problem that the CO output in the exhaust gas cannot be accurately detected by the sensor output. Therefore, normally, the sensor output of the CO sensor in the exhaust gas and the true CO in the exhaust gas are
The concentration relationship graph data can be calculated in advance, for example, for city gas.
A fuel gas such as 13 A is produced as a representative, and the sensor output detected from the CO sensor is collated with the graph data to detect the CO concentration in the exhaust gas.

[0007]

The fuel for combustion equipment is
In addition to gases such as 6A, 6B, and 13A, various gases such as butane gas and propane (LPG) gas are used.
The present inventor notices that the components of various gases are different, and burns various gases to contain H ₂ contained in the exhaust gas.
The gas concentration was measured. As a result, it was found that the H ₂ concentration in the exhaust gas differs depending on the gas species.

Conventionally, it is assumed that the H ₂ gas concentration in the exhaust gas does not differ depending on the type of combustion gas (gas type), and the sensor output and the exhaust CO concentration are based on one of the representative gases. Related data was required. However, in practice, for example, as shown in FIG. 7, the gas species of the fuel is different, also the value of the sensor output is the same, it is assumed that the CO concentration in the exhaust gas varies, for example, the sensor output is V _b In this case, a difference in CO concentration of ΔU _b occurs between the 6B gas and the propane gas, and the relationship graph data between the sensor output and the CO concentration in the exhaust gas is obtained by using one representative gas. In the method of using, there was a problem in that the CO concentration in the exhaust gas could not be detected accurately because variations occurred for different gas types.

Therefore, the inventor of the present invention does not use the graph data obtained from one type of gas, but obtains the relational data between the sensor output and the CO concentration in advance for each gas type and uses it for combustion. We propose a method to specify the gas type at the initial setting, check the sensor output of the CO sensor with the related data of the specified gas type during operation, and detect the CO concentration in the exhaust gas based on the related data. ing.

However, in the above-mentioned proposed method, relational data for a large number of gas items are obtained and given, and further,
You have to specify the gas type to use at the time of initial setting,
There is a problem that it takes time.

Further, even if the same kind of gas is used, the output of the CO sensor is used for the combustion equipment as in the method proposed above because there are subtle variations in the gas components depending on the gas supply source (for example, gas cylinder). There is a problem in that the actual CO concentration and the detected CO concentration vary even when compared with the data of the gas type to be used, and the accurate CO concentration cannot be detected.

The present invention has been made in order to solve the above problems, and its purpose is to make it possible to easily detect an accurate CO concentration in exhaust gas regardless of the type of gas used. An object is to provide a device for detecting exhaust gas CO concentration of equipment.

[0013]

In order to achieve the above object, the present invention is constructed as follows. That is, the first aspect of the present invention is to provide two catalytic combustion reaction type CO sensors installed on the exhaust side of a combustion device, a sensor drive control unit for electrically heating the two CO sensors to different operating temperatures, and true CO concentration by removing of H ₂ density component of the CO density component and H ₂ concentration component contained in the sensor output using an operating temperature different two CO previously given arithmetic expression captures the sensor output of the sensor And a CO concentration determination calculation unit that calculates and outputs a value.

A second aspect of the present invention is one contact-reaction type CO sensor installed on the exhaust side of the combustion equipment, and a sensor for heating by energizing the CO sensor by alternately switching to different operating temperatures at predetermined time intervals. removing a drive control unit, the concentration of H ₂ component of the CO density component and H ₂ concentration component contained in the sensor output using the capture previously given arithmetic expression the sensor output of the CO sensor at different operating temperatures before and after the switching And a CO concentration determination calculation unit that calculates and outputs a true CO concentration value.

[0015]

In the present invention having the above structure, when the device is driven,
For example, the sensor drive control unit electrically heats the two CO sensors to different operating temperatures, and the CO concentration determination calculation unit takes in the sensor outputs of the two CO sensors. An arithmetic expression is given to this arithmetic unit in advance, and this arithmetic expression uses sensor outputs from two CO sensors having different operating temperatures to produce sensor outputs regardless of the type of fuel used in the combustion equipment. The contained H ₂ concentration component is removed, and the value of the CO concentration in the exhaust gas is calculated. From this, the above two C
By substituting the sensor output of the O sensor into the arithmetic expression of the arithmetic unit irrespective of the gas type, it becomes possible to simply and accurately calculate and output the true CO concentration value in the exhaust gas.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In the description of each embodiment, the same reference numerals are given to the same names as in the conventional example, and the duplicated description will be omitted.
Further, in each of the embodiments described below, the combustion device is a combustion device such as a water heater as in the conventional example.

The inventor of the present invention burns various gases used in the water heater and uses the catalytic combustion reaction type CO sensor 13 as shown in FIGS.
Sensor output component and the concentration of the (CO density component) and H ₂ concentration sensor output amount of (H ₂ density component) was measured. As a result, it was discovered that the ratio between the CO concentration component and the H ₂ concentration component contained in the sensor output is determined only by the operating temperature (energized heating temperature) of the sensor, regardless of the gas species used in the water heater. did.

As shown in FIG. 3, when the operating temperature of the CO sensor 13 rises, the sensor output voltage corresponding to the H ₂ gas increases, and when the CO sensor 13 is heated to 170 ° C. (heating by energization), The output voltage related to H ₂ gas is CO
The ratio of the CO concentration component and the H ₂ concentration component contained in the sensor output of the CO sensor 13 is 1 to 1, which is the same as the output voltage involving the gas, but the CO concentration and the H ₂ concentration do not change. When the CO sensor 13 is heated to 230 ° C., the output voltage involving H ₂ gas becomes twice the output voltage involving CO gas, and the CO concentration component and H ₂ contained in the sensor output.
The ratio with the concentration component is 1: 2. Further, although not shown, when heating the CO sensor 13 to 350 ° C.
_The output voltage of the 2 gas involved is 5 times the output voltage of the CO gas involved, and the ratio between the CO concentration component and the H ₂ concentration component is 1: 5.

As described above, it was found that the ratio between the CO concentration component and the H ₂ concentration component contained in the sensor output for each operating temperature of the CO sensor 13 was constant regardless of the gas species.

The inventor has found that the ratio between the CO concentration component and the H ₂ concentration component contained in the sensor output of the CO sensor 13 is C
A device that detects the true CO concentration in exhaust gas by using the outputs of two CO sensors 13 having different operating temperatures, paying attention to the fact that it is constant regardless of the gas species for each operating temperature of the O sensor 13. Invented

FIG. 1 is a block diagram showing the structure of an exhaust CO concentration detecting device for a combustion device according to the first embodiment. The exhaust CO concentration detection device for the combustion equipment of this embodiment is 2
Individual CO sensors 13A and 13B, a sensor drive control unit 14,
The CO concentration determination calculation unit 15 and
The concentration confirmation calculation unit 15 is connected to the CO safety device 16 of the combustion equipment.

The two CO sensors 13A and 13B have the same constructions as shown in FIGS. 4 and 5 and are installed on the exhaust side of the water heater.

The sensor drive controller 14 includes a CO sensor 13A,
CO sensors 13A and 13A for heating 13B by energization
Power supply circuit 18 for supplying a current to B, and a control circuit for controlling the on / off operation of the power supply circuit and the amount of supply current of the power supply circuit
19 and a distribution circuit 20 that distributes and supplies a current to the CO sensors 13A and 13B. Sensor drive controller
Reference numeral 14 controls the amount of current supplied to the CO sensors 13A and 13B during sensor operation to maintain different operating temperatures of the CO sensors 13A and 13B, respectively. In this embodiment, the CO sensor 13A has a preset operating temperature of 230 ° C.
The supply current amount is controlled so that the sensor 13B is energized and heated to a set operating temperature of 350 ° C. which is different from the operating temperature of the CO sensor 13A.

The CO concentration determination calculator 15 has a built-in memory, and an arithmetic expression for accurately calculating the true CO concentration x in the exhaust gas is obtained and given to this memory as follows.

The above equation can be derived based on the ratio between the CO concentration component and the H ₂ concentration component at each operating temperature of the CO sensor 13, as shown in FIG. As mentioned above, regardless of the type of gas used in the water heater, the operating temperature of 230
C contained in the sensor output a of the CO sensor 13A at ℃
The ratio between the O concentration component and the H ₂ concentration component is 1: 2, and the ratio between the CO concentration component and the H ₂ concentration component contained in the sensor output b of the CO sensor 13B at the operating temperature of 350 ° C. is 1/5. . From this, the true CO concentration in the exhaust gas can be calculated as x (pp
m) and the H ₂ concentration is y (ppm), the CO sensor
The sensor output a of 13A is expressed as a = k ₁ · (x + 2y), and the sensor output b of the CO sensor 13B is b = k ₂ · (x
+ 5y) can be represented. However, k ₁ and k ₂ are conversion constants of the sensor output, and are obtained in advance by experiments or the like.

Solving for the CO concentration x from the simultaneous equations of the above two equations, the arithmetic expression for calculating the true CO concentration x by removing the H ₂ concentration y is x = (5a / 3k ₁ )-(2
b / 3k ₂ ).

As described above, the value of the true CO concentration x in the exhaust gas is calculated based on the ratio between the CO concentration component and the H ₂ concentration component at each operating temperature of the CO sensor 13 shown in the graph of FIG. The calculation formula to be performed is derived, and the derived calculation formula is given to the memory.

The CO concentration determination calculation unit 15 includes a CO sensor 13A.
The sensor output a and the sensor output b from the CO sensor 13B are fetched, the arithmetic expression is read from the memory, and the sensor outputs a and b are substituted into the above arithmetic expression to calculate the true CO concentration x value. The signal of the calculated fixed value of the CO concentration is C
It is output to the O safety device 16.

The CO safety device 16, for example, stops the combustion of the water heater when the definite value of the CO concentration exceeds a previously given dangerous value, or adds up the definite value of the CO concentration every time it is sampled. CO safe operation is performed in various processing modes, such as stopping combustion when the integrated value reaches a preset dangerous concentration.

According to the present embodiment, by simply substituting the sensor outputs a and b of the two CO sensors 13A and 13B having different operating temperatures into the calculation formula of the CO concentration determination calculation section 15, the exhaust gas can be easily obtained. The true CO concentration inside can be calculated and output.
The above calculation formula is for CO of all gas types used in the water heater.
Since it can be applied to gas detection, it is not necessary to obtain and provide data and calculation formulas for each gas type, and it is possible to detect an accurate CO concentration regardless of gas type by giving only one calculation formula. Is possible. Therefore, the CO of the CO safety device 16
Safe operation can be performed accurately and CO in the water heater
The reliability of safe operation can be improved.

FIG. 2 is a block diagram showing the configuration of the exhaust CO concentration detecting device for the combustion equipment according to the second embodiment. In the description of the second embodiment, the same reference numerals will be given to the same names as those in the first embodiment, and the duplicated description will be omitted.

In this embodiment, only one CO sensor 13 as shown in FIGS. 4 and 5 is installed on the exhaust side of the water heater. The sensor drive controller 14 is a power supply circuit similar to that of the first embodiment.
The control circuit 19 includes a timer 18 and a control circuit 19. This control circuit 19 switches the supply current amount in the same manner as in the first embodiment by switching the CO sensor 13 at a preset time interval so as to alternately energize and heat the set operating temperature of 230 ° C. and 350 ° C., for example. Control the operating temperature of the CO sensor 13.

The same formula as in the first embodiment is obtained and given to the CO concentration determination calculation unit 15. This calculation unit 15 reads the operating temperature information of the CO sensor 13 from the sensor drive control unit 14, Operating temperature before and after switching 230 ° C and 35
The sensor outputs a and b of the CO sensor 13 at 0 ° C. are taken in, and the sensor outputs a and b are substituted into the arithmetic expression as in the first embodiment to calculate the definite value of the CO concentration, and the CO safety device 16 The CO safety device 16 performs the CO safety operation when the CO concentration becomes a dangerous concentration.

According to this embodiment, it is possible to obtain the same excellent effect as that of the first embodiment by installing only one CO sensor 13.

The present invention is not limited to the above-mentioned embodiments, but various embodiments can be adopted. For example,
In each of the above embodiments, the operating temperature of the CO sensor 13 is set to 230 ° C.
Although it is set to 350 ° C., two different operating temperatures such as 170 ° C. and 200 ° C. may be set, and an arithmetic expression for calculating the CO concentration is calculated according to these set operating temperatures. It is given to the CO concentration determination calculation unit 15.

Further, in each of the above-described embodiments, one arithmetic expression for calculating the CO concentration is provided in the memory of the CO concentration determining arithmetic unit 15, but various combinations of operating temperatures of the CO sensor 13 are various. Alternatively, a large number of arithmetic expressions may be derived and these plural arithmetic expressions may be given to the memory. In such a case, when a situation occurs in which the combination of the operating temperatures of the CO sensor 13 is changed, it is possible to instantly correspond an arithmetic expression according to the changed combination of the operating temperatures.

Further, in each of the above-mentioned embodiments, the hot water supply device has been described as the combustion device, but the invention is applied to various other combustion devices using gas as fuel, such as bath heaters, air conditioners, air conditioners, and heaters. It is what is done.

[0038]

According to the present invention, an arithmetic expression for calculating the true CO concentration value is given in advance to the CO concentration determination arithmetic unit, and regardless of the type of fuel used by the combustion equipment,
By substituting the values of two sensor outputs of CO sensors having different operating temperatures into the above equation, the value of the true CO concentration is calculated and output, so there is no need to give data for each gas type. Even if the proportion of H ₂ gas in the exhaust gas differs depending on the type of fuel, it is possible to accurately calculate CO in the exhaust gas without being affected by the variation in the H ₂ gas concentration between the gas types. It is possible to easily detect the concentration value. Further, based on the accurate detected value of the CO concentration, the combustion device can accurately perform the CO safe operation, and the reliability of the CO safe operation can be improved.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an exhaust CO concentration detection device for a combustion device according to a first embodiment.

FIG. 2 is a configuration block diagram of an exhaust CO concentration detection device for a combustion device in a second embodiment.

FIG. 3 is a graph showing the relationship between the operating temperature of the CO sensor and the CO concentration component and H ₂ concentration component contained in the sensor output.

FIG. 4 is a structural explanatory view of a general catalytic combustion reaction type CO sensor.

5 is an explanatory view of a state in which the CO sensor of FIG. 4 is disassembled.

6 is a circuit diagram of CO detection of the CO sensor shown in FIG.

FIG. 7 is an explanatory diagram showing a conventional problem.

[Explanation of symbols]

 13 CO sensor 14 Sensor drive control unit 15 CO concentration determination calculation unit

Claims (2)

[Claims] 1. A catalytic combustion reaction type two CO sensors installed on the exhaust side of a combustion device, a sensor drive control unit for electrically heating the two CO sensors to different operating temperatures, and the operating temperature of the two CO sensors. The sensor output of two different CO sensors is taken in, and the CO concentration component contained in the sensor output and the H ₂ concentration component of the H ₂ concentration component are removed by using a given arithmetic expression to calculate the true CO concentration value. An exhaust gas CO concentration detection device for a combustion device, comprising an output CO concentration determination calculation unit. 2. A contact-reaction type CO sensor installed on the exhaust side of a combustion device, and a sensor drive control unit for alternately switching the CO sensor to a different operating temperature at a predetermined time interval and heating it by energization. , The CO output of the CO sensor at different operating temperatures before and after the switching is taken in, and the H ₂ concentration component is removed from the CO concentration component and the H ₂ concentration component contained in the sensor output using a predetermined arithmetic expression to obtain a true C
An exhaust gas CO concentration detection device for a combustion device, comprising: a CO concentration determination calculation unit that calculates and outputs an O concentration value.